This invention relates to polymeric compositions and their preparation, which compositions when cured have an integral permanently tacky surface layer, and more particularly to self-adhering polymers used as prosthetic appliances.
Our society places a heavy emphasis on physical attributes. Because of this, a person with a congenital, developmental, or acquired defect may be considered by some as socially unacceptable subconsciously, if not overtly. Such defects also affect a person's self-image. Since facial appearance and expression are both highly visible and a primary means of communication, defects of the head and neck areas are more socially traumatic than defects of other body parts. The preparation of maxillofacial prosthetics requires the use of both art and science in reconstructing defects using polymeric synthetic materials The goal of maxillofacial prosthetics is establishing function, fit, appearance, and physiology.
There are two general categories of maxillofacial prosthetics, namely, intraoral and extraoral. Intraoral prostheses are usually fabricated in association with a partial or complete denture. Retention of intraoral prostheses usually pose few problems except in a completely edentulous patient having markedly resorbed ridges, poor quality bony or soft tissue undercuts, and a bulky or weighty obturator. Extraoral prostheses pose more retentive as well as aesthetic problems. A major problem for a patient wearing an extraoral prosthetic device is the potential for dislodgement, and concomitant patient embarassment during normal activity.
A number of different types of polymeric materials have been utilized as base materials for prostheses. Principal among these polymers have been the silicone rubbers and polyurethanes. These elastomeric polymers are used for most extraoral prostheses because of the life-like qualities that can be imparted to them. These qualities include flexibility and the ability to be colored. This coloring is accomplished by adding fibers or pigment to the prepolymer or by tattooing the completed prostheses to conform them closely to the skin tones of the areas contiguous to the reconstructive site.
The chemical inertness of these polymers once cured is a major factor in their popularity in maxillofacial prosthetic reconstruction. However, the same chemical inertness and inherently non-stick properties which makes polymers such as silicone rubbers desirable prosthetic materials also is the cause of the majority of difficulties in working with them. While in some cases the use of surgery to provide tissue undercuts to aid in mechanically retaining a prosthesis is possible, in many other cases adhesives alone, or in combination with other mechanical retention aids such as wires, elastics, or eyeglasses, must be used as the primary means for retention. For example, a prosthetic ear may have virtually no other means for retention than an adhesive. This is also true in most cases where the defect is large or cannot be surgically modified to provide mechanical retention.
At the present time, we know of no completely satisfactory and medically safe adhesive for routinely securing, and regularly detaching for hygienic purposes, prosthetic devices. The problems of applying adhesives to and retaining them on inherently non-stick surfaces, such as silicone rubber, are readily apparent. These problems are compounded by the presence of surface contaminants such as dirt, oils, and dead skin on the tissue to which the prosthetic device is to be applied. Once cured, many adhesives no longer are sticky and will not bond again after removal. Also, many adhesives that have pressure sensitive properties lose their adherent properties once their surface has been contaminated.
Accordingly, the need exists in the art for medically acceptable polymer compositions suitable for use as prosthetic devices which possess permanently adherent, properties and which can be repetitively applied and detached from human skin or other surfaces.